Coal Industry (Patents) Limited

David James Martin

A leaky-feeder or other form of guided radiocommunication system serving a linear route or track is equipped at intervals with static marker devices which successively modify a radio signal passing those points between a fixed base station and a personal or mobile station travelling the route. By reference to the resulting overall modification to the signal as received at the mobile or fixed station the position of the mobile station may be determined or delimited.

Vehicle location system

The position of an object which moves along a fixed path is determined by measuring the phase displacement of two signals received from demodulators connected to an aerial located along the path. A transmitter carried by the objects feeds signals to the demodulators and one of these sends a demodulated signal direct to a comparator while the other sends its signal to the comparator along the aerial.

Apparatus for determining the position of a object

A leaky feeder radio transmission system uses twin feeders connected respectively to a transmitter and receiver at a base station. The feeders are connected at intervals by uni-directional amplifiers which, alternately along the lines, are connected for conduction in opposite directions. Filters are positioned in the line between amplifier connection points. A mobile station adjacent to the feeders receives signals at one frequency from the feeders and transmits signals at a second frequency.

Communication system between a transmitter, receiver station and a

A telecommunication system used in a mine has a long aerial along a tunnel which radiates signals to a mobile station. Signals from the station are radiated back to the line. Repeaters are included along the line to make up power losses. A connection of an extra length of line is made on the output side of each repeater and extends back parallel to the line for a distance of up to half the distance between adjacent repeaters. This extra line reduces the attenuation of signal power between repeaters.

Radiating telecommunication systems

A telecommunication system uses a long main transmission line which extends from a base station and has repeaters along its length. A parallel line is divided into sections corresponding in length to the distance between repeaters. Selected sections are connected in parallel with the main line through switches which operate at about a 3 kHz frequency. The switching operation reduced alternations in the main signal and mitigates problems arising from standing waves.

Radiating telecommunication systems switching

A leaky feeder coaxial cable has the inductance of the outer conductor altered by winding an extra conductor on the outer conductor or by physically forming the outer conductor so that it is unsymmetrical.

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Leatherhead, United Kingdom

David James Martin